KR20080064133A - Organic EL light emitting device - Google Patents

Abstract

According to the present invention, the first unit light emitting device 10 is interposed between the first lower electrode 12 and the first upper electrode 16 via the first organic light emitting layer 14 and the first upper electrode 16. The second lower electrode 22 and the second upper electrode 26, which are connected or are made of the same material as the first upper electrode 16, to the second unit light emitting device 20 via the second organic light emitting layer 24. The organic electroluminescent device 1 in which two unit light emitting elements which are formed are juxtaposed in parallel, and the first and second unit light emitting elements 10 and 20 exhibit different emission colors.

Description

Organic EL light emitting device {ORGANIC EL LIGHT EMITTING DEVICE}

The present invention relates to an organic EL (electroluminescent) light emitting device having a low total driving voltage and excellent in white uniformity.

The organic EL device is (i) a self-luminous device, (ii) can be driven at a low DC voltage, and (iii) various emission colors such as red, green, blue or white by selecting an organic EL material or device structure to be used. It is characterized by the fact that it is feasible. For this reason, it is attracting attention not only as next generation display technology but also as a large area lighting technology in recent years.

When the structure of an organic EL element is largely divided, it is divided into a lower emission type and an upper emission type. The lower emission type is, for example, a structure in which a transparent electrode such as indium tin oxide (ITO) is provided on a light-transmitting support substrate such as glass, and an organic light emitting layer and a counter reflective electrode are sequentially stacked thereon. The light generated in the organic light emitting layer is extracted to the outside of the device through the transparent support substrate. On the other hand, the upper emission type is a structure in which a reflective electrode is provided on a supporting substrate, and an organic light emitting layer and an opposing transparent electrode are sequentially stacked thereon, and the light generated in the organic light emitting layer is not the supporting substrate side but the opposite transparent electrode side. It is taken out from. In addition, in the upper emission type, the opposing transparent electrode is formed as a light transflective and semireflective electrode to form a microcavity structure. By selecting the distance between the reflective electrode and the opposing electrode, the light generated in the organic light emitting layer is amplified, and high intensity light is emitted to the outside of the device. The technique to take out is examined (patent document 1).

In addition, white light is indispensable for the lighting technology. As a white light emitting organic EL element, the technique of laminating | stacking the some light emitting layer which emits a different color from the above-mentioned organic light emitting layer is examined. For example, Patent Literature 2 discloses a technique in which the organic light emitting layer is formed of two layers, a blue light emitting layer and an orange light emitting layer, such as a hole transporting layer, a blue light emitting layer, an orange light emitting layer, and an electron transporting layer. In patent document 3, the technique of laminating | stacking the light emitting layer of RGB primary colors like the hole injection layer / hole transport layer / red light emitting layer / blue light emitting layer / green light emitting layer / electron injection layer is disclosed.

In the case where a planar light source is to be manufactured using the organic EL element as described above, the simplest configuration is a configuration in which the organic light emitting layer is sandwiched by upper and lower electrodes to cover the entire light emitting surface. In this configuration, however, (i) the voltage drop in the electrode portion, in particular the transparent electrode portion, does not result in a uniform current density throughout the light emitting surface, and therefore luminance unevenness occurs in the plane, and (ii) flows into the light emitting portion. Joule heat is generated by concentrating the current to the wiring part connecting the light emitting part and the driving power source. (Iii) When conduction between the upper and lower electrodes occurs at any place within the light emitting surface, the current applied to this conducting point is concentrated. Therefore, there existed a subject that the circumference | surroundings of a conduction part will not be shiny.

Among these problems, (i) and (iii) can be solved by using matrix electrodes that are orthogonal to each other, and by arranging auxiliary wiring having low resistance so as to conform to the matrix electrodes. However, it did not improve on task (ii).

When the current density when the voltage V is applied to the organic EL element is J, J and V have a non-linear relationship, for example, J = A · V ⁿ (A: proportionality constant, n> 1). Increasingly increases the current density J rapidly. Here, if the area of the light emitting portion is S, the current flowing through the entire light emitting portion is SJ. This current concentrates on the wiring portion connecting the light emitting portion and the driving power source, and Joule heat is generated, causing thermal degradation of the wiring portion.

Reducing the resistance of the wiring portion is one means of reducing the Joule heat generated in the wiring portion. However, there is a space limitation in the wiring portion inside the illumination light source, which makes it difficult to reduce the resistance. Therefore, in order to apply an organic electroluminescent element by large area illumination, the technique of reducing the current density J which flows through an organic electroluminescent light emission part was desired.

As a technique of lowering this current density J, some techniques are disclosed. Patent Literature 4 discloses a technique of laminating an organic light emitting layer in an energization direction via an intermediate conductive layer. Among these, patent document 5, patent document 6, etc. are disclosed about the stacked element which laminate | stacks an organic light emitting layer in an electricity supply direction.

The stacked element in which the organic light emitting layer is laminated in the energization direction has a structure in which an organic EL light emitting layer of N layers is overlapped via a connection layer. By doing so, the driving voltage becomes N times but the luminance becomes N times with the same current value. If the luminance is the same as that of the element of the first layer, the voltage is 1 time and the current value is 1 / N times. Therefore, when compared with the same luminance, the row of lines in the wiring portion can be reduced to 1 / N. However, as a connection layer for supplying a carrier to an adjacent organic light emitting layer, a method of using a metal thin film, a method of using an inorganic material, a method of doping an organic material for generating a carrier, and the like are disclosed. It was difficult to realize a carrier balance that evenly and uniformly emits light. In addition, in order to obtain white light emission which is important as illumination, it was necessary to laminate organic light emitting layers having different colors. In this case, since the organic material used in each light emitting layer is different, it was more difficult to adjust favorable carrier balance. In addition, there is a problem that the distance between the electrodes is increased for stacking the N layers, and the optical interference is difficult to be optimized, the light extraction efficiency is difficult to increase, and the luminous efficiency is difficult to increase.

In addition, Patent Document 4 discloses a technique for juxtaposing an organic EL element in parallel in a light emitting surface. The same technique is disclosed in Patent Document 7. In particular, in Patent Document 7, as shown in Fig. 14, for example, three unit organic EL elements have three lines connected in series, and each of these three lines is configured to color different colors. By configuring the three lines to emit three primary colors of blue, green, and red, respectively, white light emission can be obtained relatively easily unlike the stack type described above. However, there existed a problem that white uniformity was insufficient, white light emission efficiency was insufficient, and driving voltage became too high.

Patent Document 1: International Publication No. WO 01/39554

Patent Document 2: Japanese Patent Laid-Open No. 2002-272857

Patent Document 3: Japanese Patent Laid-Open No. 2004-006165

Patent Document 4: Japanese Patent Application Laid-Open No. 11-329748

Patent Document 5: Japanese Unexamined Patent Publication No. 2003-045676

Patent Document 6: Japanese Patent Application Laid-Open No. 2004-342614

Patent Document 7: US Patent Application Publication No. 2004/0032220

An object of the present invention is to provide an organic EL light emitting device having a low total driving voltage and excellent white uniformity.

<Start of invention>

As a result of intensive studies by the present inventors, it has been found that the problem can be solved by setting the emission colors of the portions connected in series to two or more different colors. In addition, two reflecting surfaces are provided for each unit light emitting element, and the distance between the reflecting surfaces is set so as to narrow the natural light emitting width of light emitted from the light emitting center included in the organic light emitting layer, thereby achieving high efficiency, and the shape of the unit light emitting element. By optimizing and further studying the arrangement of different colors, it has been found that an organic EL light emitting device having a low total driving voltage and excellent white uniformity can be obtained.

According to a first aspect of the present invention, there is provided a first unit light emitting device having a first organic light emitting layer interposed between a first lower electrode and a first upper electrode, and a material electrically connected to the first upper electrode or the same material as the first upper electrode. An organic EL light emitting device is disclosed in which a second unit light emitting element with a second organic light emitting layer interposed in planar view between a second lower electrode and a second upper electrode, wherein the two unit light emitting elements exhibit different light emission colors.

According to a second aspect of the present invention, there is provided a first unit light emitting device having a first organic light emitting layer interposed between a first lower electrode and a first upper electrode, and a material electrically connected to the first upper electrode or the same material as the first upper electrode. Between the second lower electrode and the second upper electrode, the second unit light emitting device via the second organic light emitting layer, the third lower electrode electrically connected to the second upper electrode or made of the same material as the second upper electrode; An organic EL light emitting device is disclosed in which a third unit light emitting element via a third organic light emitting layer is planarly juxtaposed between the third upper electrodes, and the three unit light emitting elements exhibit two or more different light emission colors.

According to a third aspect of the present invention, when N is an integer of 2 or more and k is an integer of 1 or more and N-1 or less, the first unit is interposed between the first lower electrode and the first upper electrode through the first organic light emitting layer. K + 1 interposed between the light emitting element and the k + 1th lower electrode and the k + 1th upper electrode which are electrically connected to the kth upper electrode or the same material as the kth upper electrode, and intersect the k + 1 organic emission layer Nth unit light emitting device having an Nth organic light emitting layer interposed between a unit light emitting device and an Nth bottom electrode and an Nth top electrode which are electrically connected to the Nth top electrode or the same material as the Nth top electrode An organic EL light emitting device including N unit light emitting elements including a plane is disposed in a plane, and the N unit light emitting elements exhibit two or more different light emission colors.

According to a fourth aspect of the present invention, at least one unit light emitting element has two light reflecting surfaces, at least one of the light reflecting surfaces has semireflective semitransmissivity, and the organic light emitting layer is located between two light reflecting interfaces. An organic EL light emitting device is disclosed in which a distance between two light reflecting interfaces is set so as to narrow a natural light emission width of light emitted from a light emitting center included in an organic light emitting layer.

According to a fifth aspect of the present invention, the shape of the light emitting surface of the unit light emitting element is a rectangular shape having a length and width of 10 or more, two adjacent unit light emitting elements are electrically connected in a rectangular longitudinal direction, and the unit An organic EL light emitting device in which an array of light emitting elements is a diagonal array is disclosed.

A sixth aspect of the present invention discloses an organic EL light emitting device having a light diffusing member on a light extraction side.

According to the present invention, an organic EL light emitting device having a low total driving voltage and excellent in white uniformity can be provided.

1 is a diagram schematically showing an organic EL light emitting device of a first embodiment according to the present invention.

FIG. 2 is a diagram schematically showing an organic EL light emitting device in which N unit light emitting elements are arranged in parallel. FIG.

FIG. 3A is a diagram illustrating a first top view of the organic EL light emitting device of FIG. 1, and FIG. 3B illustrates a second top view of the organic EL light emitting device of FIG. 1.

FIG. 4 is an enlarged view of a part of the diagonal arrangement in FIG. 3B. FIG.

Fig. 5 is a diagram showing a half width in an organic EL light emitting device having two or more light reflecting surfaces.

Fig. 6 is a diagram showing a half width in an organic EL light emitting device having only one light reflecting surface.

7 is a graph comparing the intensities of the spectra A ', B, and C when the same current density is applied.

8 is a diagram schematically showing an organic EL light emitting device of a second embodiment according to the present invention.

9 is a diagram illustrating a top view of the organic EL light emitting device of FIG. 8.

(A)-(E) is a figure which shows typically the method for manufacturing the organic electroluminescent device of FIG.

Fig. 11 is a diagram showing a mask in which an opening is formed on a diamond blade.

12 is a diagram schematically showing an organic EL light emitting device of a third embodiment according to the present invention.

Fig. 13 is a diagram showing a radiation pattern showing the angle dependency of the light emission intensity.

Fig. 14 is a diagram showing an organic EL light emitting device in which a conventional organic EL element is arranged in parallel in a light emitting plane.

Best Mode for Carrying Out the Invention

1. First embodiment

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically 1st Embodiment of this invention.

As shown in this figure, the organic EL light emitting device 1 has a first unit light emitting element 10 and a second unit light emitting element 20 arranged on a substrate 100.

The first unit light emitting element 10 has a structure in which the first lower electrode 12, the first organic light emitting layer 14, and the first upper electrode 16 are stacked in this order on the substrate 100.

The second unit light emitting device 20 has a structure in which the second lower electrode 22, the second organic light emitting layer 24, and the second upper electrode 26 are stacked in this order on the substrate 100.

The first and second lower electrodes 12, 22 function as anodes for injecting holes into the organic light emitting layer, or cathodes for injecting electrons into the organic light emitting layer. When the first lower electrode 12 is an anode, the second upper electrode 26 is a cathode, and when the first lower electrode 12 is an anode, the second upper electrode 26 is an anode. In the present embodiment, the first lower electrode 12 and the second upper electrode 26 are electrically connected. Since the lower electrode and the upper electrode have different polarities, the first unit light emitting element 10 and the second unit light emitting element 20 are connected in series. Here, the first lower electrode 12 and the second upper electrode 26 may be different materials through the connecting portion, or may be made of the same common material.

In addition, the first organic light emitting layer 14 and the second organic light emitting layer 24 emit light of different colors. When using as white illumination, it is preferable to select, for example, a combination of blue and yellow, a combination of cyan and red red, and the like.

The organic EL light emitting device of the present embodiment may include N units (N is an integer of 2 or more) of the first unit light emitting element 10 and the second unit light emitting element 20. At this time, as shown in FIG. 2, it is preferable to arrange N elements which the upper electrode and the lower electrode of the adjacent element are connected. N is usually 2 to 10.

As shown in this figure, the first unit light emitting element 10, the k + 1th unit light emitting element 60, and the Nth unit light emitting element 80 are juxtaposed on the substrate 100. k is an integer of 1 or more and N-1 or less.

The first unit light emitting device 10 is as described above.

The k + 1 th light emitting device 60 includes a k + 1 th lower electrode 62, a k + 1 th organic light emitting layer 64, and a k + 1 th top electrode 66 on the substrate 100 in this order. It has a laminated structure as it is.

In this embodiment, the kth lower electrode (not shown) and the k + 1th upper electrode 66 are electrically connected. Here, the kth lower electrode and the k + 1th upper electrode 66 may be different materials through the connecting portion, or may be made of the same common material.

The Nth unit light emitting device 80 has a structure in which an Nth lower electrode 82, an Nth organic light emitting layer 84, and an Nth upper electrode 86 are stacked in this order on the substrate 100.

In the present embodiment, the N-th lower electrode (not shown) and the N-th upper electrode 86 are electrically connected. Here, the N-th lower electrode and the N-th upper electrode 86 may be different materials through the connecting portion, or may be made of the same common material.

There are various methods of arranging the first unit light emitting element 10 and the second unit light emitting element 20. For example, FIGS. 3A and 3B are top views of the organic EL light emitting device according to the first embodiment. In this figure, an arrangement of elements of four columns and four rows is shown. A1 to A4 are first unit light emitting devices, and B1 to B4 are second unit light emitting devices. A and B denote that the emission colors are different.

In Fig. 3A, the unit in which four unit light emitting elements A1, B2, A3, and B4 are connected in series is one row, and four rows are connected in parallel to the driving power supply V. In Fig. 3A, the emission colors A and the emission colors B are arranged in a row, respectively, in the vertical column. In Fig. 3B, the light emission colors A and B are alternately arranged in the vertical column as in the horizontal row. The arrangement shown in Fig. 3B is called "diagonal arrangement", and the color mixture of the emission colors A and B is high, and when the combination of A and B is made white, the uniformity and visibility of the white Excellent and preferred.

4 is an enlarged view of a part of the diagonal arrangement of FIG. 3 (B). In this embodiment, it is preferable that each unit light emitting element A1, B2, B1, A2 is rectangular, and is connected in series in the rectangular long side direction. In addition, when the length of the long side of each unit light emitting element is H and the length of the short side is V, it is preferable that the ratio of H / V is 3.5 or more. By doing in this way, the number of unit light-emitting elements connected in series can be reduced, and a drive voltage can be included in a realistic range. More preferably, it is 5 or more, More preferably, it is 5-10.

This point is demonstrated concretely below. In lighting and display, it is necessary to consider the mixing distance according to the screen size and the use. The mixed color distance is an indicator of how uniformly mixed colors appear when they fall away from the screen when light emitting pixels (light emitting elements) of different colors are juxtaposed. For example, a mixed color distance of about 12 m pitch is about 5 m. do. For example, consider forming a light emitting surface having a square diagonal of 5 inches. In order to suppress the mixed color distance on the light emitting surface by about 30 cm, the pitch of light emitting elements emitting different colors needs to be 12 mm / 5 m × 30 cm = 0.72 mm or less. Therefore, when the light emitting unit elements are set to 0.72 mm square shape, it is necessary to arrange 90 unit parts of light emitting units of 90 mm / 0.72 mm = 125 on one side of 5 inches (one side 90 mm) diagonally. In this embodiment, an organic EL element is used as the light emitting element. Since a practical brightness (for example, 1000 cd / m 2 or more as luminance) is required in an organic EL element, at least 3 V or more voltage is required, so that 125 unit light emitting elements in series are 125 × 3 V = 375 V. A voltage of 300 V or higher is required and becomes impractical. On the contrary, when it wants to suppress it to 100 V or less general for home use, 100 V / 3 V = 33 or less series connection numbers. In this case, the length of the unit light emitting element in the series connection direction needs to be 90 mm / 33 pieces = 2.7 mm or more. On the other hand, since the mixed color distance is 30 cm or less, the short side of the unit light emitting element needs to be 0.72 mm or less, and the ratio between the long side and the short side of the unit light emitting element is preferably about 3.5 or more. Although the light emitting surface of 5 inches diagonal has been described as an example, considering that the mixed color distance can be set in proportion to the area of the light emitting surface, the ratio of the short side to the long side is set to 3.5 or more in the light emitting surface of any size. desirable.

In addition, in the present embodiment, the first unit light emitting element 10 and the second unit light emitting element 20 emit light of different colors. In order to emit light of a different color, (i) the light emitting material used for an organic light emitting layer is changed, (ii) it is set as the organic light emitting layer containing light emission components of two or more colors, and color adjustment effect by a color filter and a fluorescent conversion layer is performed. There exists a method of taking out a different color using them. Among these, in this embodiment, it is preferable to use the light emitting material different from the method of (i), ie, two unit light emitting elements.

In a particularly preferred embodiment in the present embodiment, two light reflecting surfaces are provided inside the unit light emitting element, at least one of the light reflecting surfaces is semi-reflective semi-transmissive, and an organic light emitting layer is provided between the two light reflecting interfaces, The form which sets the distance between two light reflection interfaces so that the natural light emission width of the light which the light emission center contained in an organic light emitting layer emits may be narrowed. In addition, at least two light reflection surfaces may be sufficient and three or more may be sufficient.

Here, the method of setting the distance between two light reflection interfaces to narrow the natural light emission width of the light emitted from the light emission center included in the organic light emitting layer will be described in detail using Alq ₃ as the light emitting medium layer.

As an element structure, an Al / ITO laminated film as an anode on a glass substrate, 4,4'-bis (N- (1-naphthyl) -N-phenylamino) biphenyl (NPD) as a hole transporting layer, and tris as a light emitting medium layer Considering (8-quinolinol) aluminum (Alq ₃ ), Alq: Li as the electron transporting layer and Mg: Ag / ITO as the cathode in that order, the device configuration is considered. Glass (0.7 mm) / Al (200 nm) / ITO (10 nm) / NPD (X nm) / Alq ₃ (30 nm) / Alq: Li (10 nm) / Mg: Ag (10 nm) / ITO (100 nm). Here, each of the interfaces between Al and ITO and the Alq: Li and Mg: Ag interfaces forms two light reflecting surfaces.

First, the organic light emitting layer is a part of NPD (X nm) / Alq ₃ (30 nm) / Alq: Li (10 nm) in this example. When the organic EL element is energized, NPD and Alq _{3 may} all shine in the organic light emitting layer, but the Alq ₃ side is overwhelmingly strong in luminescence intensity. The light emission center contained in an organic light emitting layer is a material which shows the strongest light emission intensity among organic light emitting layers. In addition, a natural light emission width means the thing of the full width at half maximum (FWHM = Full Width at Half Maximum) in the light emission spectrum of the thin film formed by the light emitting material used as a light emission center alone, or a lean solution. By narrowing this natural light emission width, the half width of the light emission extracted from an organic EL element is made narrower than the natural light emission width.

For this purpose, the distance between two light reflection surfaces can be selected. For example, when the film thickness X of NPD is 60 nm in the said specific example, the case where 205 nm is considered is considered. At this time, the distance between the two light reflection surfaces is 110 nm and 255 nm, respectively. At this time, the relationship between the natural light emission width of Alq which is a light emission center, and the half width of the light emission from the organic electroluminescent element when it is set to X = 60 nm and 205 nm is shown in FIG.

In Fig. 5, A is the light emission spectrum of the thin film of Alq ₃ which is the emission center, B is the EL spectrum when NPD film thickness X = 60 nm, and C is the EL spectrum when NPD film thickness X = 205 nm. Indicates. It is the spectrum normalized by the maximum peak intensity, respectively. At this time, the half widths f _A , f _B , and f _C of the spectra A, B, and C are f _A = 120 nm, f _B = 74 nm, and f _C = 45 nm, respectively.

On the other hand, the relationship between the width of the natural emission and the width of the EL spectrum in the device configuration having only one light reflection surface will be described. As the device configuration, the following device configuration is considered, in which ITO as an anode, NPD as a hole transport layer, Alq ₃ as a light emitting medium layer, Alq: Li as an electron transport layer, and Al as a cathode are laminated in this order on a glass substrate. Glass (0.7 mm) / ITO (130 nm) / NPD (60 nm) / Alq ₃ (40 nm) / Alq ₃ : Li (20 nm) / Al (200 nm). Here, only the interface between Al and Alq ₃ : Li forms a light reflection surface. 6 is a graph comparing the light emission spectrum (A) of the Alq ₃ thin film as the emission center and the EL spectrum (A ′) of the organic EL element. The half width of the EL spectrum A 'is f _A' = 112 nm. As can be seen from Fig. 6, when only one light reflecting surface is retained, there is almost no change in the natural emission width and the half width of the EL spectrum even if the film thickness of each layer is adjusted in any way.

7 is a graph comparing the intensities of the spectra A ', B, and C when the same current density is supplied.

As can be seen from Fig. 7, by making the half-width of the EL spectrum narrower than the natural light emission width, the maximum peak intensity becomes larger than when only one light reflection surface is retained, and the original light emission color indicated by the light emission center can be enhanced.

In the present embodiment, the first unit light emitting element 10 or the second unit light emitting element 20 or both have two light reflecting surfaces, and the light emission width can be narrowed for each light emission.

2. Second Embodiment

It is a schematic diagram which shows 2nd Embodiment of this invention.

As shown in this figure, the organic EL light emitting device 2 differs from the first embodiment only in that it has a third unit light emitting element 30. That is, the organic EL light emitting element 2 includes the first unit light emitting element 10 juxtaposed on the substrate 100, the second unit light emitting element 20, and the third unit light emitting element 30. In addition, since the 1st unit light emitting element 10 and the 2nd light emitting element 20 are the same as that of Embodiment (1) mentioned above, description is abbreviate | omitted.

The third unit light emitting device 30 has a structure in which the third lower electrode 32, the third organic light emitting layer 34, and the third upper electrode 36 are stacked in this order on the substrate 100. The second lower electrode 22 and the third upper electrode 36 are electrically connected. Here, the second lower electrode 22 and the third upper electrode 36 may be different materials through the connecting portion, or may be made of the same common material.

The first, second, and third unit elements emit two or more different colors. Preferably, the three unit light emitting devices emit three primary colors of different colors, for example, blue, green, and red. By doing in this way, it becomes possible to realize the white light-emitting light source which balances three primary colors of blue, green, and red.

The organic EL light emitting device of the present embodiment may also include N (N is an integer of 2 or more) of the first unit light emitting element 10, the second unit light emitting element 20, and the third unit light emitting element 30. At this time, as shown in FIG. 2, it is preferable that N elements which the upper electrode and the lower electrode of the adjacent element are connected are arranged.

The arrangement of the first unit light emitting element 10, the second unit light emitting element 20, and the third unit light emitting element 30 is various. For example, FIG. 9 is a top view of a light emitting surface of the organic EL light emitting device of the second embodiment. In this figure, an arrangement of elements of six columns and six rows is shown. A1 to A6 are first unit light emitting elements, B1 to B6 are second unit light emitting elements, and C1 to C6 are third unit light emitting elements. Reference signs A, B and C indicate that the emission colors are different.

As shown in FIG. 9, three types of unit light emitting elements A, B, and C are connected in series in the energization direction. The energization direction is preferably a so-called Diagonal arrangement in which pixels emitting different colors, such as A, B, and C, are also arranged in the vertical direction.

Such an organic EL light emitting device can be manufactured, for example, as follows. FIG. 10 is a diagram schematically showing a method for manufacturing the organic EL light emitting device of the second embodiment. First, a common lower electrode is formed on the support substrate 100 (Fig. 10 (A)). Subsequently, the lower electrode patterns 12 and 22 are patterned by a method suitable for the material of the lower electrode, and correspond to the lower electrodes of the first to third unit light emitting devices 10, 20, and 30, respectively. , (32) was obtained (Fig. 10 (B)). Subsequently, insulating layers a and b are provided to ensure insulation between the lower electrode and the upper electrode (Fig. 10 (C)). For example, after forming a photoresist film in the whole surface, only the insulating layer a is formed through an exposure, image development, and peeling process, and after forming a photoresist film again, the insulating layers a and b pass through the same process, and an insulating layer b can be formed and installed. Subsequently, organic light emitting layers 14, 24, and 34 are formed independently according to materials and film thicknesses designed for each of the first to third unit light emitting devices 10, 20, and 30. (FIG. 10 (D)). Here, in order to make the planar arrangement of the first to third unit light emitting elements 10, 20, and 30 into a diagonal arrangement as shown in FIG. 9, for example, as shown in FIG. This can be achieved by preparing a mask in which an opening is formed in a high blade shape, and then proceeding the vapor deposition step one by one or by one row. Next, upper electrodes 16, 26, and 36 of the first to third unit light emitting elements 10, 20, and 30 are formed (FIG. 10E). Here, the second upper electrode 26 is electrically connected to the first lower electrode 12, and the third upper electrode 36 is electrically connected to the second lower electrode 22.

Also in this embodiment, any one or more or all of the first, second and third unit light emitting elements 10, 20, 30 have two light reflecting surfaces, and the light emission width for each light emission. You can also narrow it.

In addition, in this embodiment, the case where the first, second and third unit light emitting elements 10, 20, and 30 emit light of three colors has been described, but four or more unit light emitting elements may be listed. When it is possible to emit light of four colors or more.

3. Third embodiment

12 is a diagram showing a third embodiment of the present invention.

As shown in this figure, in the third embodiment, in the organic EL light emitting device of the second embodiment, the light diffusing member 40 is provided on the light extraction side rather than the upper electrode of each unit light emitting element. .

Fig. 13 is a diagram showing a radiation pattern showing the angle dependence of the light emission intensity in the above-described organic EL device in which Alq ₃ is a light emitting medium layer. The radiation pattern in the case where the NPD film thickness is 60 nm and 205 nm, respectively, is B ', C, and the radiation pattern in the case where only one light reflection layer is A'. As can be seen from Fig. 13, in a configuration in which two light reflecting surfaces are provided and the half width of the EL spectrum is narrower than the natural light emitting width of the emission center, radiation tends to concentrate on the front (normal direction of the light emitting surface). Depending on the application, it may be necessary to reduce the concentration on the front. In that case, the function of the light diffusing member provided on the light extraction side can be alleviated with an isotropic radiation pattern without losing the light intensity.

In addition, in all the above-described embodiments, the k + 1 upper electrode is connected to the k lower electrode, but the k + 1 lower electrode may be connected to the k upper electrode (the same if the viewpoint is changed).

The main member which forms the light emitting device of this invention is demonstrated.

1.light reflecting surface

The light reflecting surface is formed of a light reflecting layer and a light semitransmissive layer, and is preferably formed of a light reflecting electrode and a light semitransmissive electrode.

(1) light reflection layer, light transflective layer

Since light is taken out and used, at least one shall transmit a part of light (semi-transmissive layer). As the material, an inorganic compound having transparency having a larger refractive index than a metal or an organic material layer can be used. In the case of metal, specular reflection by a metal surface occurs, and in the case of an inorganic compound having a refractive index larger than that of an organic material layer, light reflection occurs according to the magnitude of the difference in refractive index. In order to make at least one side semi-permeable, these film thicknesses are made small or the difference of refractive index is adjusted.

(2) light reflective electrode

When the light reflective electrode is an anode, a function of supplying the voltage from the power source for driving the organic EL element to the organic EL element and injecting holes into the hole injection layer is required, so that the low resistance and high work function (for example, , 4.0 eV or more), metals, alloys, electrically conductive compounds, or mixtures or laminates thereof.

Specifically, indium tin oxide (ITO), indium zinc oxide (IZO), CuI (copper iodide), SnO ₂ (tin oxide), zinc oxide, gold, silver, platinum, palladium, aluminum, chromium, nickel and the like It can be used individually by 1 type or in combination of 2 or more types.

When the light reflective electrode functions as a cathode, it is preferable to use a metal, an alloy, an electrically conductive compound or a mixture thereof having a small work function (for example, less than 4.0 eV) so as to have good electron injection property.

Specifically, one kind of magnesium, aluminum, indium, lithium, sodium, cesium, silver or the like may be used alone or in combination of two or more kinds thereof.

In addition, ultrathin films of these metals and metal oxides such as aluminum oxide, and ultrathin films of halides of alkali metals such as lithium and cesium can also be used.

The light reflectance with respect to the light taken out of the element outside of the light reflective electrode is preferably 30% or more, and more preferably 50% or more.

(3) light transflective electrode

The light semitransmissive electrode is formed by laminating a layer containing a material having high light transmissivity such as ITO and a thin film layer containing a material having high light reflectivity such as metal, among the materials exemplified in the light reflective electrode, or a material having high light reflectivity. The thing of the thin film layer single layer containing these can be used. When the light reflective electrode is an anode, the light semitransmissive electrode is a cathode. When the light reflective electrode is a cathode, the light semitransmissive electrode is an anode.

Since the light reflecting layer has a function of receiving charges from one side thereof and emitting charges from the other side, it is necessary to be electrically reflective at the same time as the light reflectivity. Therefore, it is preferable that a light reflection layer is a metal film or a semiconductor film. Among these, a metal film is preferable from the viewpoint that the visible light region from blue to red can realize a high reflectance in a wide range.

The reflectance of the metal film is determined by the film thickness d, the complex refractive index n-i 占, and the surface roughness (RMS roughness) σ. As a preferable material of a metal film, it is preferable that both the real part n of a complex refractive index and the virtual part k (corresponding to light absorption coefficient) are small. Specifically, Au, Ag, Cu, Mg, Al, Ni, Pd, these alloys, etc. are mentioned. When the film thickness d is thin, light transmits and the reflectance becomes small.

Although it depends also on the value of the complex refractive index part (k) of the metal species to be used, it is preferable that it is 5 nm or more as a film thickness of a light reflection layer.

In addition, when the surface roughness σ is large, since light is diffusely reflected and there is less component reflected in the direction perpendicular to the light emitting surface of the organic EL element, the surface roughness σ is preferably less than 10 nm, more preferably less than 5 nm. .

The light transmittance with respect to the light taken out of the element of a light semitransmissive electrode becomes like this. Preferably it is 30% or more, More preferably, it is 50% or more.

Moreover, the light reflectance with respect to the light taken out of the element of a light semitransmissive electrode becomes like this. Preferably it is 20% or more, More preferably, it is 40% or more.

2. Organic light emitting layer

The organic light emitting layer includes an organic light emitting medium layer, and includes a hole transporting layer, an electron transporting layer, and the like, as necessary.

(A) Blue light emitting layer

The blue light emitting layer includes a host material and a blue light dopant.

The host material is preferably a styryl derivative, an anthracene derivative or an aromatic amine. It is particularly preferable that the styryl derivative is at least one kind selected from among distyryl derivatives, tristyryl derivatives, tetrastyryl derivatives and styrylamine derivatives. It is preferable that an anthracene derivative is an asymmetric anthracene type compound. It is preferable that an aromatic amine is a compound which has 2-4 aromatic-substituted nitrogen atoms, and the compound which has 2-4 aromatic-substituted nitrogen atoms and has at least one alkenyl group is especially preferable.

The compound mentioned above is specifically described in Japanese Patent Application No. 2004-042694.

It is preferable that it is at least 1 sort (s) chosen from a styryl amine, an amine substituted styryl compound, an amine substituted condensed aromatic ring, and a condensed aromatic ring containing compound as a blue type dopant. At that time, the blue dopant may be composed of a plurality of other compounds. Examples of the styrylamine and the amine-substituted styryl compound include compounds represented by the following formulas (1) and (2), and compounds represented by the following formula (3) as the condensed aromatic ring-containing compound.

[Wherein, Ar ³ , Ar ⁴ and Ar ⁵ each independently represent a substituted or unsubstituted aromatic group having 6 to 40 carbon atoms, at least one of which contains a styryl group, and p represents an integer of 1 to 3; Indicated]

[In the formula, Ar ⁶ and Ar ⁷ are each independently an arylene group having 6 to 30 carbon atoms, E ¹ and E ² are each independently an aryl group or alkyl group having 6 to 30 carbon atoms, an alkyl group, a hydrogen atom or a cyano group Q represents an integer of 1 to 3, and U and / or V are substituents containing an amino group, and preferably the amino group is an arylamino group.]

[Wherein A is an alkyl or alkoxy group having 1 to 16 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted alkylamino group having 6 to 30 carbon atoms, or carbon Substituted or unsubstituted arylamino group having 6 to 30 atoms, B represents a condensed aromatic ring group having 10 to 40 carbon atoms, and r represents an integer of 1 to 4]

(B) green light emitting layer

The green light emitting layer includes a host material and a green dopant.

It is preferable to use the same host material as the host material used as the blue light emitting layer.

Although there is no restriction | limiting in particular as a dopant, For example, the coumarin derivative disclosed in Unexamined-Japanese-Patent No. 0281381, Unexamined-Japanese-Patent No. 2003-249372, etc., the aromatic amine derivative connected with substituted anthracene structure, and amine structure can be used, for example. have.

(C) orange to red light emitting layer

The orange to red light emitting layer includes a host material and an orange to red light dopant.

As a host material, it is preferable to use the same thing as the host material used for a blue light emitting layer.

As the dopant, a fluorescent compound having at least one fluoranthene skeleton or a perylene skeleton, for example, the following chemical formula can be used.

[Wherein, X ²¹ to X ²⁴ are each independently an alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and X ²¹ and X ²² and / or X ²³ and X ²⁴ May be bonded via a carbon-carbon bond or -O-, -S-. X ²⁵ to X ³⁶ is a hydrogen atom, a straight, branched or cyclic alkyl group having 1 to 20 carbon atoms, a straight, branched or cyclic carbon atom having 1 to 20 alkoxy groups, substituted or unsubstituted 6 to 30 carbon atoms Aryl group, substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, substituted or unsubstituted arylamino group having 6 to 30 carbon atoms, substituted or unsubstituted alkylamino group having 1 to 30 carbon atoms, substituted or unsubstituted An arylalkylamino group having 7 to 30 carbon atoms or a substituted or unsubstituted alkenyl group having 8 to 30 carbon atoms in the ring, and adjacent substituents and X ²⁵ to X ³⁶ may be bonded to each other to form a cyclic structure. At least one of the substituents X ²⁵ to X ³⁶ in each formula preferably contains an amine or alkenyl group.]

3. Light diffusing member

In the configuration in which two light reflecting surfaces are provided and the half width of the EL spectrum is narrower than the natural light emission width of the light emission center, the radiation tends to concentrate forward (normal direction of the light emitting surface). The light diffusing member can have a function of alleviating the concentration in the front, and a known member can be used. For example, the following members can be used.

1) A member in which beads having a particle size equal to the wavelength of visible light (any material is transparent) are arranged on the substrate surface.

2) Micro lens arrays with tens of micrometer pitch. As the shape of the micro lens, a cone, a triangular cone, a square cone, or the like can be selected.

3) A member formed of a layer of low refractive index silica airgel

Example 1

An organic EL light emitting device in which a first unit light emitting device that emits blue, a second unit light emitting device that emits green, and a third unit light emitting device that emits red are disposed on a plane of 0.7 mm in thickness, in a plane. The size of the light emitting screen is square of 45 mm 2, and the size of the light emitting surface of the unit light emitting element is H = 2.0 mm, V = 0.4 mm, h = 0.25 mm, v = 0.1 mm in FIG. 4. That is, 20 unit light emitting elements are connected in series in the long side direction of H = 2.0 mm.

In addition, the structure of the compound used for the element is shown below.

[Manufacture of Lower Electrode Substrate]

On the glass support substrate of thickness 0.7mm, ITO was formed into a film at 100 nm thickness by sputtering as an adhesion layer. Thereafter, Ag was formed into a film of 150 nm by sputtering, and ITO was formed into a film of 10 nm by sputtering. The lower electrode was patterned by the photolithography so that the line / space in the transverse direction was 2.15 / 0.10 and the line / space in the longitudinal direction was 0.42 / 0.08. In addition, after spin-coating an arc-related resist (V259PA, manufactured by Shin-Nitatsu Furniture Co., Ltd.), an ultraviolet light exposure and development was performed through a photomask covering the edge of the lower electrode pattern, and then fired under conditions of 180 ° C. to insulate the insulating film. A lower electrode substrate was prepared.

[Preparation of Vacuum Deposition Apparatus]

The lower electrode substrate was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes, and then UV ozone cleaning for 30 minutes. The lower electrode part substrate after cleaning was attached to the substrate holder of the vacuum deposition apparatus.

In addition, HT as a hole transporting material, BH as a host material of a light emitting medium layer, BD as a blue light emitting material, GD as a green light emitting material, RD as a red light emitting material, and a buffer layer were previously applied to each molybdenum heating boat. LiF was used as a material, and Mg and Ag were respectively mounted as a light semitransmissive semireflective material, and the ITO target was mounted in a separate sputtering apparatus as a light transmissive electrode.

[Production of First Unit Light-Emitting Element]

First, a 130 nm HT film | membrane which functions as a positive hole transport layer was formed. Subsequent to film formation of the HT film, Compound BH and Compound BD were co-deposited at a film thickness of 30 nm so as to have a film thickness ratio of 30: 1.5 as a blue light emitting layer. On this film, an Alq ₃ film was formed to a film thickness of 20 nm as an electron transporting layer. Thereafter, LiF was deposited at a thickness of 1 nm as a buffer layer, and a Mg: Ag film functioning as a light semitransmissive semi-reflective layer was deposited at 10 nm with a film-forming ratio of Mg and Ag of 9: 1, Furthermore, ITO which functions as a light transmissive electrode was formed into a film of 100 nm in thickness.

[Production of Second Unit Light-Emitting Element]

First, the HT film | membrane which functions as a positive hole transport layer was formed into 170 nm. Subsequent to film formation of the HT film, Compound BH and Compound GD were co-deposited at a film thickness of 30 nm so as to have a film thickness ratio of 30: 0.4 as the green light emitting layer. On this film, an Alq ₃ film was formed to a film thickness of 20 nm as an electron transporting layer. Subsequently, LiF was deposited as a buffer layer at a film thickness of 1 nm, and a Mg: Ag film functioning as a light semitransmissive semireflective layer was deposited at 10 nm with a film-forming ratio of Mg and Ag of 9: 1, Furthermore, ITO which functions as a light transmissive electrode was connected to the lower electrode of a 1st unit light emitting element, and it formed into a film in thickness of 100 nm.

[Manufacture of Third Unit Light-Emitting Element]

First, 60 nm of the HT film | membrane which functions as a positive hole transport layer was formed. Subsequent to film formation of the HT film, Compound BH and Compound RD were co-deposited at a film thickness of 30 nm so as to have a film thickness ratio of 30: 1.5 as a green light emitting layer. As the electron transporting layer, an Alq ₃ film was formed _{on the} film at a film thickness of 20 nm. Thereafter, LiF was deposited at a thickness of 1 nm as a buffer layer, and a Mg: Ag film functioning as a light semitransmissive semi-reflective layer was deposited at 10 nm with a film-forming ratio of Mg and Ag of 9: 1, Furthermore, ITO which functions as a light transmissive electrode was connected to the lower electrode of a 2nd unit light emitting element, and it formed into a film in thickness of 100 nm. The organic EL light emitting device was obtained as described above.

[Evaluation of Organic EL Light Emitting Device]

When a current was passed through this terminal portion, the entire surface emitted light. The current density flowing in each unit light emitting element when the brightness was adjusted to 1000 cd / m 2 was 7.9 mA / cm 2, and the total driving voltage was 81 V. FIG. The chromaticity was (0.314, 0.356) white light, the current efficiency was 17.8 cd / A, and the power efficiency was 13.9 lm / W.

The organic EL light emitting device of the present invention can be used for backlight of a liquid crystal display, decorative lighting, indoor general lighting and the like.

Claims (6)

A first unit light emitting device having a first organic light emitting layer interposed between the first lower electrode and the first upper electrode; A second unit light emitting element electrically connected with the first upper electrode or between the second lower electrode and the second upper electrode, which are the same material as the first upper electrode, with a second organic light emitting layer interposed in plan view, The organic electroluminescent device of which the first and second unit light emitting elements have different emission colors. A first unit light emitting device having a first organic light emitting layer interposed between the first lower electrode and the first upper electrode; A second unit light emitting device electrically connected to the first upper electrode or interposing a second organic light emitting layer between a second lower electrode and a second upper electrode which are the same material as the first upper electrode; A third unit light emitting element which is electrically connected to the second upper electrode or between the third lower electrode and the third upper electrode, which is the same material as the second upper electrode, and is interposed in plan view, And the first, second and third unit light emitting elements exhibit at least two or more different emission colors. When N is an integer of 2 or more and k is an integer of 1 or more and N-1 or less, A first unit light emitting device having a first organic light emitting layer interposed between the first lower electrode and the first upper electrode; A k + 1th unit light emitting element electrically connected to a kth upper electrode or interposed between a k + 1th lower electrode and a k + 1th upper electrode which are the same material as the kth upper electrode and a k + 1th organic emission layer; , N pieces including an Nth unit light emitting element interposed between an Nth lower electrode and an Nth upper electrode which are electrically connected to the Nth upper electrode or the same material as the Nth upper electrode; Unit light emitting elements are arranged in a plane; And the N unit light emitting elements exhibit two or more different light emission colors. The method according to any one of claims 1 to 3, wherein at least one unit light emitting element has two light reflecting surfaces, At least one of the light reflecting surfaces is semi-reflective semi-transmissive, The organic light emitting layer is positioned between two light reflecting interfaces, The organic electroluminescent device in which the distance between two light reflection interfaces is set so that the natural light emission width of the light emitted by the light emission center contained in an organic light emitting layer may be narrowed. The shape of the light emitting surface of the said unit light emitting element is a rectangle of any one of Claim 1 to 4 which consists of a rectangle of 3.5 or more length, Two adjacent unit light emitting elements are electrically connected in a rectangular longitudinal direction, An organic electroluminescent device in which the array of unit light emitting elements is a diagonal array. The organic electroluminescent device according to any one of claims 1 to 5, which has a light diffusing member on a light extraction side.

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